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Changes in the O2-Hb dissociation curve:

الكلية كلية طب حمورابي     القسم الكلية ذات القسم الواحد     المرحلة 2
أستاذ المادة امجد حسن عباس المنصوري       11/10/2017 15:11:30
Changes in the O2-Hb dissociation curve:
Shift to the right:
Occur when there is decreased affinity of Hb for O2 and unloading of O2 in the tissues is facilitated.

Factors causing right shift:
Increases in PCO2 and decreases in pH: When metabolic activity of the tissues increase, production of CO2 increases. An increase in tissue PCO2 causes an increase H+ and a decrease pH. This mechanism ensures that O2 delivery to the tissues can meet O2 demand (e.g. in exercising skeletal muscle).
Bohr effect states that an increased H+ concentration causes a right shift of the O2-Hb dissociation curve which causes Hb to unload O2 more readily in the tissues.
Increases in temperature. Increases in temperature also cause right shift, and facilitate unloading of oxygen in the tissues.
Increases in 2, 3 diphosphoglycerate (2,3-DPG) concentration.
2,3,-DPG: Is a byproduct of anaerobic glycolysis, present in high concentration in red blood cells because of their content of 2,3-DPG mutase, it diminishes the affinity of hemoglobin for O2, 2,3-DPG binds to ?-chains of deoxyhemoglobin and reduces their affinity for O2. This decrease in affinity causes right shift and facilitates unloading of oxygen in the tissues. 2,3-DPG production increases under hypoxic conditions as in high altitude which causes hypoxemia, which stimulates production of 2,3-DPG in red cells. This facilitates O2 delivery to the tissues as adaptive mechanism.
Importance: Hypoxic condition that last longer than a few hours…
Disadvantage: The excess DPG also makes it more difficult for the hemoglobin to combines with O2 in the lungs.


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